摘要
广东南雄盆地广泛分布着白垩纪红色地层,厚5千多米,面积约1 020 km2。前人普遍认为该套地层属山间盆地河湖相碎屑沉积,同时在湖底还沉积了大量钙质结核及多层泥灰岩。野外观察发现,地层中红颜色随层理/层次变化也发生深浅变化,说明地层的红色是与层理同期形成,属沉积阶段的原生色。所谓湖底沉积结核及泥灰岩实为红色古土壤层中的钙结核与钙板层。磁性矿物测量表明,地层中的主要载磁矿物为赤铁矿,且相对含量较黄土-古土壤高得多,表明该地层是长期处于地表高温干旱氧化环境中形成。红色粉砂层和黏土层中发育的钙质结核及钙板层与古近系红黏土类似,属土壤淀积层,位于土壤黏化层下部。因此,南雄盆地白垩纪红层的"水成"只是局部或者短暂特点,总体是地表干旱氧化条件下经成土作用形成的红色土壤序列。
Cretaceous red strata are widely distributed in Nanxiong Basin, Guangdong province, with a thickness of 5 961 m and an area of 1 020 km^2. Previous studies held that they were fluvial and lacustrine deposition in the intermontane basin and a lot of calcium nodules and muddy limestone layers were deposited in the lake. However, in the field investigation, we found that the shading of the red color changed with the stratification, indicating that the color forming is synchronous with the stratification during the deposition. The rock magnetism measurement showed that hematite dominated in the layers, whose content was several times higher than that in Quaternary paleosols. In general, such high content of hematite were associated with arid and oxidizing environment. Moreover, calcium nodules and calcareous plates in the silt and clay layers, similar to those in the Paleogenered clay, form a paleosol sequence in Cretaceous. Therefore, the Cretaceous red strata in Nanxiong Basin were actually palaeosol sequences that formed under long-term arid and oxidizing environment. The underwater environment was just local and temporary.
出处
《亚热带资源与环境学报》
2016年第3期29-37,共9页
Journal of Subtropical Resources and Environment
基金
国家自然科学基金项目(41210002、U1405231)
福建省属公益类科研院所基本科研专项(2016R1032-3)的资助
关键词
南雄盆地
白垩纪红色地层
岩石磁学
赤铁矿
沉积环境
Nanxiong Basin
Cretaceous red stratum
rock magnetism
hematite
sedimentary environment
